Ultra high frequency oscillation generator



Dec. 17, 1946. J. R. FORD IGH FREQUENCY OSCILLATION GENERATOR ULTRA HFiled Feb. 5, 1944 2 sheets-sheet 1 9 QXWG x -L s 1w NSQKY AIV Arme/vihDef, A17, 1946. 1R. @RD 2,412,805

lULTRA HIGH FREQUENCY OSCILLATION GENERATOR Filed Feb. 5, 1944 2Sheets-Sheet 2 CA 73900 E Amaai a4 mobs INVENTOR. J'aH/l ,9. Paca BYPatented Dec. 17, 1946 UNITED STATES PATENT OFFICE "ULTRA VHIGHFREQUENCY OSCILLAT'ION GENERATOR John R. Ford, 'Narberth, Pa., assignorto Radio Corporation of America, -a-corporation of Dela- WareApplication vFebruary 5, 1944, Serial No. 521,179

(Cl. Z50-36) '11 Claims.

reasonably constant output level over its entire V"range, in which bothfeed back and'frequency of "operation are adjusted simultaneously by Va,single control.

megacycles and having 'a frequency range of vthree or four to one.

A further object is to providean ultra high freemploying a lighthousetube Almere complete description ofthe invention A'follows inconjunction with drawings, wherein: Fig. `1 is a view, partly yincross-section, of an ultra high 'frequency oscillator system embodyingthe principles of the invention;

Fig. 2

is a perspective view of that portion of,

' ment used in both tube I of generally known rternal Vcircuit of thislighthouse the grid tubular conductor forming the common wall of the twoconcentric resonators and 'which llllm'tllbe;

Fig. 3'is a cross-section of the slider resonators; and 6 show,.diagrammatically only,

arrange- Figs. 4, 5 and positions along The Aaverage pocathode and ganisgraphically illustrated for'the different slider positions.

Referring `to Fig, 1, there is shown a vacuum lighthouse type,

nators with the sliders in different the lengths of the conductors.

elements. VIn practice, the anode, cathode andgrid electrodes within'theevacuated glassenvelope are positioned 'very close to each other. Theanode within the tubeforms one en'd lof 'a metallic cylinder which isconnected to `the General Electric type GLI-446 triode. The details tubeare now well known in the art and described in Electronic Industry,September, 1944, page 178; and in Science News The cathode for the radiofrequency energy flowing between the grid G and conductor 4. Theresonatorformed of conductors 3, ll is tunedby means of slider 6 whichis a circular aiairengaging the inner surface of 3 and the outerv`surface of ll. Conductor 4 is hollow and accommodates in its interiora hollow "cylindrical lcon- 'ductor 5 which is capacitively coupled atone end to the anode ring A. The ring A is separated from the conductor5 by means of a mica spacer 1 which comprises part of a by-passcondenser for radio frequency energy flowing between the anode A andconductor 5. The inner surface of conductor l! forms with conductor 5 aconcentric line resonator which is tuned by means of av circularmetallic slider 6' engaging both conductors Il and 5. It should be notedthat sliders 6 and 6 for the different resonators are staggered inposition. The two sliders B and I' are unicontrolled over links 9 andsuitable gearing I5 operated by a handle H.

Conductor 4 which forms a common conductor for both resonators isprovided at one end with a plurality of slots 8 for capacitivelycoupling both resonators together externally of the tube I. Slider 5 isadjustable over the entire length of the slots 8, thus adjusting theeffectiveness of these slots. Stated in another way, the slider B isadjustable from a point near the grid electrode where there would be nocapacity coupling through the slots to a point well beyond the slotswhere the slots are completely effective.

A grid leak resistor R shunts the condenser formed by the grid ring Gand the spaced tubular grid conductor ll. Anode polarizing potential issupplied from a source B+ to the anode via a rod II. High energy lossmaterial, such as iron dust core I2, surrounds the rod II and isinsulated from the tubular anode conductor 5 by means of an insulationtube II3 which may be paper. This iron dust core prevents the radiofrequency energy from iiowing along rod II. If desired, the iron dustcore can be replaced by conducting rubber. The means for keeping thevacuum tube I in position has not been shown for the sake of simplifyingthe drawing, although it will be understood that such means may includesuitable springs for exerting pressure on the socket of the vacuum tubein the direction of the line resonators.

The construction of the slots in the grid line conductor li isillustrated in more detail in Fig. 2. The construction of the sliders Iiand 6 is illustrated in Fig. 3 which shows a cross-section of one ofthese sliders. The effective length of the slider 6 is such that it cansubstantially completely cover the slots 8 in the grid line 4 whenApositioned. at the extreme left of Fig. 1.

In the operation of the oscillator shown in Fig. 1, there is always somecapacity feed back between the two resonators 3, II and 4, 5 through theinterelectrode capacities of the tube I. The

slots 8 in tubular conductor i augment this interelectrode capacitycoupling to a desired degree. The slots serve to boost the feed back atthe lower frequencies of operation and also decreases the tendency forthe oscillator to produce oscillations at higher modes of oscillation.This is Ashown more clearly by reference to Figs. 4, 5 and 6 which showthe sliders 6 and 6 in three different positions along the lengths ofthe resonators, and also snow the average potential Ear-Ic across theslots between anode and cathode conductors 5 and 3, respectively.

With an oscillator of the type shown in Fig. 1 operating over afrequency range from 400 megacycles to 1500 megacycles, the illustrationof Fig.

4 shows the arrangement of the sliders 6 at a point near the gridelectrode where the slots Il are ineffective to provide capacitycoupling therethrough. The slider 6, it will be seen, covers the slotsand shields the resonators from each other. The yonly feed back whichexists in this case is now through the vacuum tube II. In thearrangement shown in Fig. 4, the oscillator produced oscillations at1500 megacycles, The voltage curve between anode and cathode for thedesired mode of oscillation is shown in the solid line immediately belowthe circuit arrangement. The arrangement of Fig. 5 shows the slots 8completely uncovered by the slider 6 which is now in a positionintermediate the ends of the cathode-grid line resonator. In thearrangement of Fig. 5, the oscillator operated at about 900 megacycles,and the average potential across the slots is shown by the solid curvewhich slopes more gradually. The dotted line curve shows the voltagethat would exist between anode and cathode for the three-quarter mode ofoscillation. The slots are positioned at a null for this last voltage.The arrangement of Fig. 5 shows the sliders in the extreme rightposition, in which location the oscillator operated at about 400megacycles. It should be noted (Fig. 6) that the average potentialacross the slots between anode and cathode conductors is close to themaximum possible, while the slots are positioned near a null for thevoltage that would exist between anode and cathode for the three-quartermode of oscillation. In Figs. 5 and 6, the three-quarter mode voltagecurves are shown dotted, while the desirable one-quarter voltages areshown in solid lines. It will be noted that the oscillator produced itshighest frequency at the one-quarter mode when the cathode-grid lineresonator is shortest, and this is the case with the slots covered overby the slider 6. Due to the loading on the resonators by the Vacuumtube, the maximum voltage (EAK) across the slots in the case of Figs. 5and 6 is a greater fraction of the voltage which would be present withno loading by the vacuum tube than that obtainable in the case of Fig.4.

In the practice of the invention, the slots are so dimensioned andpositioned that feed back at the desired frequency of oscillations isconsiderably greater than that for higher frequencies corresponding tohigher modes of oscillation. Because of the greater feed back at thedesired frequencies, the oscillator is constrained to generateoscillations at only the desired frequency. The slots are preferablylocated near or at a voltage (anode-cathode) maximum point for thedesired mode of oscillation, which point is also a voltage minimum forthe undesired mode, thus providing a considerable difference in feedback for the two modes. To obtain the Ygreatest benefits of theinvention, this difference in feed back between the cases of the desiredmode and the undesired mode should be the greatest possible, althoughthe benefits of the invention'can be achieved so long as there is anyappreciably greater feed back at the desired mode than at the undesiredmode. The slots should be located near the grid electrode, as shown, inorder to obtain a wide range of frequencies by adjusting the position ofthe sliders. However, if it is desired to obtain only a single frequencycorresponding to, let us say, the thirdharmonic of the lowest frequency,then the slots should be positioned near the end of the grid linefarthest removed from the vacuum tube, and in this position the greatestfeed back will be at the higher mode (third harmonic) of oscillation,and oscillation will take place only at the higher mode. The exactposition of the slots and their exact dimensions are best determined byexperiment .sin order to obtain themaximumeifectfat-fthese fianode,vwhereby 'sa-id last two conductors form .higher frequencies. Y A -vutput fromitheoscillator maybe .taken from mon wall with said .rstresonator, said coinprobe l.I3rconnectedtotheiinnerconcluctorof-a Ainonwall having a plurality of Aslots ltherecoaxial line M.

.In -one embodiment successfully Ytried `Yout Vin *feedback between saidtwo resonators, a'tuning gpr-actice, thetuned'grid-anode Vlineresonator-had 'slider forsaid nrst resonator adjustable'in posia 4surgeimpedance -of forty '-ohms, 7while the `tion between-.the hollowconductors of said lfirst tuned grid-cathoderesonator'had'atwentyiohm--resonator .fand having such aXial length as 'to ,surge impedance.AThese lines Awere about seven 10 control the .coupling between saidresonators :inches long. vThe anode was :byepassed to .the through fsaidslots, 'said :slider in fone .position irad-iotfrequenoy anode conductor5 by a 150g/lf. iendering `said slots completely ineffective, andconcentric capacitor `"I egrid was -connected-by anotherltunine sliderfor said other resonator.

means of an annular spring to the tubular grid An oscillation generatorcomprising a vacconductor through an annular three plate `cal5 uum tubehaving grid, anode and cathode elec pacitor, the annular spring formingthe central trades, a concentric line resonator having an `plateaof the`capacitor. ."I'FwdOS annular-.mica outer l:hollow conductor coupled tovsaid :cathode discs .served as :the :,dielectrlc. One :disc lwas rand1an inner hollowf'conductor coupled `to said painted'fa :thinlineofaquadagtomakefai5000 grid, another hollow conductor coaxially rar-`ohm ggridleak. the :grid l'conductor 4 had six V'20 4ranged within`said last conductor'and coupled slots 3/8 -wide :starting Yat fthe gridcondenser to said anode, whereby said last two conductors .and .runningl away from lthe vacuum tube. form `another concentric line resonatorhaving The B+ supply lwas 250 volts positive impressed -a common wallwith said first resonator, said `on conductor Il through .;a 5600 oresistor. common lwall having a plurality of slots theree osccillatorsystem vhad a frequency `range :35 through .arranged symmetricallyaround one porfiom 400 mcfto 1200 inc. on thereof to enable feed backbetween said i Y atis-clailned is: wo resonators, a tuning slider forsaid nist oscillation generator coinnrising a vacresonatoi adlustable inposition over the length uum tube having grid, anode and cathode elec ofsaid resonator for controlling the effective .trodes, sa rc'oncentricline `resonator:coupled be- :l0 ness of said slots, said .sliderhaving-a length .connecting together rthe .inner 'and outer yicon- 40concentric line resonator having-an outer hollow 1 Ycoupled at one endto said anode, whereby said 2 An oscillation generator compmsing avaclast two conductors forma concentric line resouum tube having gridanode and cathode elecnator having a common wall with said rst tweensaid grid and cathode, another concentric o of slots therethrough nearthe end coupled to 5U any desired frequency at which the resonatorshaving such axial length as to control the couare tuned to beone-quarter wavelength long pline between said resonators through SaidSlots, electrically is greater than for any higher mode said slots beingso positioned and dimensioned of oscillation,

duce a desired frequency of operation, the volt- 55 uum tube havinggrid, anode and cathode elecage across said slots is appreciably greaterfor trodes, a concentric line resonator having an the desired frequencythan for any other mode outer hollow conductor coupled to said cathodeof oscillation. v and an inner hollow conductor coupled to said Anoscillation generator comprising aivacgrid, another hollow conductorcoaxially aruum tube having grid, anode and cathode elec- To rangedwithin said last conductor and coupled trodes, a concentric lineresonator having an to said anode, whereby said last two conductorsouter hollow conductor coupled to saidfcathode form another concentricline resonator having back between said two resonators, a tuning slider-polarizing potential to said anode, a metallic cyfor said firstresonator being adjustable in posilindrical tuning slider for each ofsaid resonation between the hollow conductors of said first tors, thetuning slider for one of said resonators resonator and having such axiallength as to conbeing adjustable in position between the hollow trol thecoupling between said resonators through conductors thereof and havingsuch axial length said slots, said slider in one position rendering asto control the coupling between said resonators `said slots completelyineffective, and another through said slots, said sliders being instaggered tuning slider for said other resonator, a conrelation, andunicontrol means for said sliders. ducting rod coaxially arranged withinthe inl0. An oscillation generator comprising a vacnermost hollowconductor of said anode-grid lo uum tube having grid, anode and cathodeelecresonator for supplying said anode with anode trodes,aconcentricline resonator having an outer polarizing potential, and high lossmaterialk surhollow conductor coupled to said cathode -and an roundingsaid rod and insulated from said innerinner hollow conductor coupled tosaid grid, anmost hollow conductor for absorbing radio reother hollowconductor coaxially arranged within .quencv energytending to flow alongsaid rod. im said last conductor and coupled to said anode,

'7. An ultra high frequency oscillation generwhereby said last twoconductors form another ator comprising a vacuum tube having grid,anconcentric line resonator having a common wall iode and cathodeelectrodes, a concentric line reswith said rst resonator, said commonwall havonator having an outer cylindrical hollow coning a'pluraltiy ofslots therethrough near one end ductor coupled at one end to saidcathode and 20 thereof to enable feed back between said two resan innercylindrical hollow conductor coupled at onators, a tuning slider forsaid i'lrst resonator the same end to said grid, a conductor coaxiallyadjustable in position over the length of said resarranged within saidlast conductor and also couonator for controlling the effectiveness ofsaid pled at one end to said anode, whereby said last slots, said sliderhaving a length which is an aptwo conductors form a concentric lineresonator preciable fraction of the length of said slots, said having acommon wall with said first resonator, slider in one position renderingsaid slots comsaid common wall having a plurality oi slots pletelyineiiective, and another tuning slider for therethrough at one portionto enable feed back said other resonaton'and means for controllingbetween said resonators, a metallic cylindrical the movement of saidsliders simultaneously.v tuning slider for each of said resonators, thetunll. An oscillation generator comprising a vacing slider for one ofsaid resonators being adjustuum tube having grid, anode and cathodeelecable in position between the hollow conductors trodes, a concentricline resonator having an outthereof and having such axial length as toconer hollow conductor coupled at one end to said trol the couplingbetween said resonators through cathode and an inner hollow conductorcoupled said slots, said sliders being in staggered relation, at itsadjacent end to said grid, another hollow and unicontrol means for saidsliders. conductor coaxially arranged within said last 8. A generator inaccordance with claim 6, conductor and coupledat its correspondinglylocharacterized in this that said high loss material cated end to saidanode, whereby said last two is an iron dust core. conductors formanother concentric line resona 9. An ultra high frequency oscillationgenera- 40 tor having a common wall with said iirst resonator comprisinga vacuum tube having grid, antor, said common wall having near its endwhich ode and cathode electrodes, a concentric line is connected to saidvacuum tube a plurality of resonator having an outer cylindrical hollowconslots therethrough to enable feed back between ductor coupled at oneend to said cathode said two resonators, a tuning slider for said firstand an inner cylindrical hollow conductor cou- "w resonatoradjustable-in position over the length pled at the same end to saidgrid, another of said resonator for controlling the effectivenesscylindrical hollow conductor coaxially arranged of said slots, saidslider having a length which is within said last conductor and alsocoupled an appreciable fraction of the length of said at one end to saidanode, whereby said last slots, said slider in one position renderingsaid two conductors form a concentric line resoo slots completelyineffective, and another tuning onator having a common wall with saidrst resslider for said other resonator, and means for onator, saidcommon wall having a plurality of controlling the movement of saidsliders simulslots therethrough at one portion to enable feed taneously.

back between said resonators, a conductor within JOHN R. FORD. saidinnermost hollow conductor for supplying

